WASHINGTON – Earlier this year, the independent commission investigating the Sept. 11, 2001, terrorist attacks played four minutes of a call from Betty Ong, a crew member on American Airlines Flight 11.

The power of her call could not have been plainer: In a calm voice, Ong told her supervisors about the hijacking, the weapons the attackers had used, the locations of their seats.

At first, Ong's reports were greeted skeptically by some officials on the ground.

"They did not believe her," said Bob Kerrey, a commission member and former senator from Nebraska. "They said, 'Are you sure?' They asked her to confirm that it wasn't air rage. Our people on the ground were not prepared for a hijacking."

For most Americans, the 9/11 attacks seemed to come in a stunning burst from nowhere.

Now, after three weeks of public hearings and a dozen detailed reports, the lengthy documentary record makes clear that predictions of an attack by al-Qaeda had been communicated directly to the highest levels of the government.

The threat reports were more clear, urgent and persistent than was previously disclosed.

Although some of the intelligence went back years, other warnings – including one that al-Qaeda seemed interested in hijacking a plane inside the United States – had been delivered to President Bush on Aug. 6, 2001, a month before the attacks.

The new information produced by the commission so far has led six of its 10 members to say or suggest that the attacks could have been prevented, though there is no consensus on when, how or by whom.

Commission Chairman Thomas Kean, a Republican and former governor of New Jersey, has described failures at every level of government, any of which, if avoided, could have altered the outcome.

Kerrey, a Democrat, said, "My conclusion is that it could have been prevented. That was not my conclusion when I went on the commission."

While the commission was created to identify mistakes and to recommend reforms, its examination has powerful political resonance. The panel has reviewed the records of two presidents, Bill Clinton and George W. Bush.

Bush, who is in the midst of a campaign for re-election, said last week that none of the warnings gave any hint of the time, place or date of an assault.

"Had I known there was going to be an attack on America, I would have moved mountains to stop the attack," he said.

Over an intense two-week stretch this month, the commission pried open some of the most closely guarded compartments of government, revealing the flow and details of previously classified information to two presidents and their senior advisers, and the performance of intelligence and law enforcement officials.

The inquiry has gone beyond the report of a joint panel of the House and Senate intelligence committee in 2002, which chronicled missteps at the middle level of bureaucracies. Urged on by a number of the families of people killed in the attacks, the Kean commission has used a mix of moral and political leverage to extract presidential communications and testimony.

Among the new themes that have fundamentally reshaped the story of the Sept. 11 attacks are:

Al-Qaeda and its leader, Osama bin Laden, did not blindside the United States, but were a threat recognized and discussed regularly at the highest levels of government for nearly five years before the attacks, in thousands of reports, often accompanied by urgent warnings from lower-level experts.

Presidents Clinton and Bush received regular information about the threat of al-Qaeda and the intention of the bin Laden network to strike inside the United States. Each president made fighting terrorism a stated priority, failed to find a diplomatic solution and viewed military force as a last resort.

At the same time, neither president grappled with the structural flaws and paralyzing dysfunction that undermined the CIA and FBI, the two agencies on which the nation depended for protection.

Even when the two agencies cooperated, the results were unimpressive. Kean said he viewed the reports on the two agencies as indictments.

Much of the debate was provoked by Richard Clarke, who led anti-terrorism efforts under Clinton and Bush and argued for aggressive action.

"Former officials, including (a National Security Council) staffer working for Mr. Clarke, told us the threat was seen as one that could cause hundreds of casualties, not thousands," according to one interim commission report.

"Such differences affect calculations about whether or how to go to war."

In the first eight months of the Bush administration, the commission found, the president and his advisers received far more information, much of it dire in tone and detailed in content, than had been generally understood.

The most dramatic came in the Aug. 6, 2001, memo presented in an intelligence briefing the White House says Bush requested. Titled "Bin Ladin Determined to Strike in US," the memo was declassified earlier this month under pressure from the commission.

After referring to a British tip in 1998 that Islamic fundamentalists wanted to hijack a plane, the memo goes on to warn: "Nevertheless, FBI information since that time indicates patterns of suspicious activity in this country consistent with preparations for hijackings or other types of attacks."

Bush has said the briefing did not provide specific details of when and where an attack might take place.

Kerrey said Bush showed "good instincts" by asking for the material, but that the call from Ong, the flight attendant on American Airlines Flight 11 – which crashed into the north tower of the World Trade Center in the day's first attack – showed that the threats and alarms were not passed down the line.

"I don't see any evidence that our airports were on heightened alert," Kerrey said. "A hijacking was not a bolt out of the blue."